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A built Vario MD 900 kit (by Vario)
The real thing in UK Air Support Colours
I
have been asked by a client to procure and build the Vario kit of
the McDonnell-Douglas 900 NOTAR Explorer helicopter, which is to be
painted in the standard UK Air Support colours of dark blue and
yellow as shown above right (looks almost black there strangely).
This is a very exciting project due to the fact that this helicopter
utilises the NOTAR system for tail control (No Tail Rotor), so
instead it uses the exhaust gases from the two turbines ducted out
of vents in the tail to control the yaw of the aircraft.
The external detail is to be as close as possible to the
aircraft shown below, including the Aircraft Registration of G-HPOL, which is quite appropriate in my
mind 
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McDonnell Douglas 900
Sunderland Police force
Call sign - OSCAR99
Registration G-HPOL
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As the kit does not use a turbine, but rather a hefty .70
nitro engine, the required jet exhaust is simulated by a powerful
fan that is ducted to the helicopters tail.
Due to this, Vario make it very clear that the model build
has to be done very carefully to keep overall weight down to the
absolute minimum if the tail control system is to work in the model
form.
You can also see that the real helicopter uses a 5 bladed head, and this
model is also going to have the 5 bladed head, which is a further
build, setup & flying challenge.
If anyone has any good photos of the UK Air
support colour schemes or better yet,
the various decals, I would really love to see them so we get it
dead right
This build will be FULLY documented here over the next few
months, with pictures, diagrams etc, so if you are interested in
this type of build, keep watching this space...
If you really want to follow along in all of the full gory
detail you can download the construction manual from Vario
themselves, or to make it easier you can just download the PDF format manual here.
September 19, 2009
The
build process has now started...
If you are thinking of building one of
these, be prepared to be very nice to your Bank Manager, as the
total estimated cost is around £3,500.00 all in.  But
WHOW!!, what a helicopter it is going to be.
All relevant parts have now been ordered from Vario, and
are expected in from Germany in about a week. Orders have also been
placed for 5 Futaba 9202 servos (to fit same all round), and a
Spektrum DX7 TX with AR7100 RX, so things are starting to
move. 
A Futaba GY401 Gyro will also be on order soon
Oh yes, and a new workbench is going to be need to be added
to the ChopperAddict workshop that will take this aircraft once the
fuselage is fully built, as it is around 6 feet long (without the 5
rotor blades)
Here is a picture of the real rotor head and the NOTAR
tail: Pretty scary eh...
 
The other quite scary thing about these helicopters is that
you need some special electronics to help you out with the
"phasing" of the main rotor blades, because with these
types of heads, the blades need to have what is known as
"precession", which means that when you put the elevator
stick forward on your TX, the swash plate will actually tilt LEFT,
and if you apply left aileron, the swash plate will tilt backwards.
The reason for this is that the blades need to get into
their correct pitch setting for the control that has been requested
by the pilot. It is quite easy to see that with 5 blades, each
individual blade is going to be doing something a little different
in terms of pitch at any given angle around the rotation. The
electronics lets you arrange this "relatively" easily.
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So this new bit of electronics
lets you feed in the correct precession settings for each
blade individually using a USB link to your PC. If you don't
get this right, the smiley on the left may well come true
when you try to spool the helicopter up...
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Well, Thursday, 24 September, 2009 dawned grey, overcast
and windy here in Lancashire, but to lighten up my day, a knock on
the door at 9:45am revealed a carrier truck bearing two rather
substantial boxes, as shown below, together with label showing they
really did come from Vario UK.
 
The boxes have a standard TV controller on the top to give some
indication of the size of the boxes.
These are not the entire delivery sadly, as both the 5
bladed head kit and the engine kit are out of stock at Vario
Germany, so they will be following along in due course, but we have
plenty now to get started on this project.
The next task is - to open them and check all parts out
very carefully...
Here is the "large" fuselage : 
and from the front
:
Basically, once built, it is going to be virtually TWICE
the length of the larger of the two boxes it came in, which is a
significant size for sure.
As you can also see, no glazing areas are cut out, or door
openings, but included in the kit are all of the glazing panels.
The quality of the mouldings at first sight seem excellent,
with a good finish, and the GRP is strong but light The boom
comes in two parts, so that you can remove the very end to access
the NOTAR mechanics if required. Equally, the top cabin mouldings
come in two parts also, which should allow fairly good access to the
mechanics.
The doors come on 2 separate pieces of GRP all shaped
nicely, but have to be cut out and then finished by the
builder. More to come on doing that task for sure. There
is in the fitting kit a nice set of scale hinges etc to mount these
really well.
CLICK HERE For a set of pictures of
the total contents of the boxes
September 23, 2009
Spent a busy day yesterday with the Dremel and a cutting
disk, removing the inner areas of the doors and cooling vents. These
are just initial cuts to give me access to the inside, so each one
still has around 1/4 inch of GRP all the way around to be cut away
once I am ready to start fitting panels etc. This sure makes it
start to look a little more like a real helicopter, rather than the
huge white whale it appears to be in the previous pictures ?
The helicopter in front is there for scale comparison, and
is one of my CopterX 450's
Sortta dwarfs the poor little CopterX doesn't it ?
And here is the view from the back quarter
CLICK HERE for more pictures of the
MD900 at this (very early) stage of the build
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Had a few spare minutes later on today, so thought I would
get the undercarriage skids prepared ready to sit the fuselage on
for more security.
There is one little catch here you need to watch out
for that the build documents do not mention, and that is that the
plastic connectors between the skid bars and the legs have a
different angle at the top because the two undercarriage struts are
at different angles when they meet this connector.
If you don't notice this you end up with skids at a very
strange angle, so it does becomes pretty obvious if you do miss
this.
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The skids are fixed to the bar connectors on the inside of
the connector with self tapping screws in the typical manner, but
for some strange reason the bar supports have to be glued into the
connectors, rather than being screwed in or bolted.
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